1. Field of the invention
The present invention relates to a headlamp for an automobile, motor cycle and motor-driven bicycle (hereinafter referred to merely as "a vehicle", when applicable), and more particularly to a projection type vehicular headlamp in which light beam emitted from a light source is reflected by a reflector, and the light beam thus reflected is irradiated through a projection lens. The projection type vehicular headlamp has been known as disclosed, for example, in U.S. Pat. Nos. 4,677,532 or 4,797,790.
2. Related art
A conventional headlamp of this type is schematically constructed as shown in FIG. 1. The light beam emitted from a light source, namely, a light bulb 2 is reflected by a reflector 3, and the light beam thus reflected is irradiated through a projection lens 4. The reflector 3 accommodating therein the light bulb 2 is unitary engaged with a lens holder 5 holding the lens 4, thus forming a projection unit 1. A clear cut forming shade 6 is provided in the lens holder 5.
The conventional headlamp described above suffers from following difficulties: The shade 6 is extended like an upright wall which blocks substantially the lower half of the section of the optical path in the lens holder 5; that is, the shade 6 disadvantageously suppresses heat convection in the projection unit 1. Hence, the heat generated by the light bulb 2 is caught behind the shade (indicated at A in FIG. 1), thus adversely affecting the radiation of heat of the projection unit 1, the lighting characteristics of the light bulb 2 acting as the light source, or a lamp body 7 surrounding the projection unit 1.